CASE REPORT

Benign nerve sheath : Atypical giant lesion in atypical location Essam Bakr, MD, Fatma Abd AlSalam, MD

Department Of Dermatology, Faculty of Medicine, Al-Azhar University, Cairo, Egypt

ABSTRACT Benign nerve sheath myxoma (myxoid neurothekeoma) is a rare benign cutaneous neoplasm of nerve sheath origin. This tumor is commonly seen in the head and neck region and sometimes in the upper extremity. The presence of myxoid neu- rothekeoma on the lower limb is seldom and rarely reported. In this report we presented a new case of myxoid neurotheke- oma in the lower limb of a 42-year-old male that showed a giant appearance.

INTRODUCTION background. Binucleated and multinucleated cells Benign nerve sheath myxoma [myxoid may be found.4 neurothekeoma (NT)] is considered one of the rare The histopathologic variants are: classic (myxoid) cutaneous neoplasm of peripheral nerve origin. It cellular and mixed types. Histologically classic was first described in 1969 by Harkin and Reed (myxoid) hypocellular variant has a well-defined as a micronodular, myxoid and loosely cellular multinodular dermal lobules composed of myxoid benign tumour of neural origin.1 Subsequently it nodules separated by fibrous septae, with nodules was identified as neurothekeoma by Gallager and having loose clusters of benign spindled-stellate Helwig in 1980.2 and epithelioid cells embedded in myxoid stroma. Neurothekeoma commonly presents as an The cellular variant has an ill-defined fascicular asymptomatic soft subcutameous nodule usualiy growth pattern consisting of plump to epitheloid on face and upper extremities. It may present as spindle cells, which may show nuclear atypia. The a painful raised, skin colored, well-circumscribed third, mixed subtype shows features intermediate lesion. It is more common in females of 21- between classic and cellular types.5 36 years, ranging in sizes between 0.5-1cm. We report a case of large-sized myxoid Clinically, a multitude of differential diagnoses neurothekeoma over the lower limb of an adult exist for NT, including , , patient and review the literature for similar cases. , neurilemomma and neurofibroma.3 The cytological features of nerve sheath CASE REPORT are less frequently documented in the past. A 42-year-old man presented with slightly However, the smears from nerve sheath myxomas painful skin lesion on the left leg for 2 years. show spindle -stellate cells and epithelioid cells The lesion started as asymptomatic small nodule with bland nuclei arranged in loose clusters, which slowly progressed and became slightly groups or whorls within a metachromatic myxoid painful during the last few months. The patient

Correspondence: Dr. Fatma Abd AlSalam, Department Of Dermatology, Faculty of Medicine, Al-Azhar University, Cairo, Egypt

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gave history of exaggerated pain during touch or dimension. The cut surface was tan yellow, with pressure on the lesion. thin white septa dividing the mass into variably Physical examination showed a solitary, raised, sized lobules. slightly erythematous large nodule of firm Histopathological examination showed a consistency measuring about 1.4 cm in diameter multilobulated dermal lesion consisting of loosely [Fig. 1]. The lesion was located on the upper arranged spindle and stellate cells within abundant part of the anterior aspect of the left leg. It was stromal mucin [Fig. 3]. Some of the cells were slightly tender on palpation with no attachment multinucleated and had hyperchromatic, irregular to the underlying structures [Fig. 2]. X-ray nuclei. Mitotic figures were rare. Many cells had studies showed a density with no bony thin, delicate net-like projections imparting a sheaf- involvement. like configuration [Fig. 4]. Immunohistochemistry The lesion was excised completely and gross showed strong immunoreactivity of infiltrating examination showed multilobulated mass, cells with S-100 stain [Fig. 5]. There was no measuring 1.4 X 1.5 X 1.2 cm in greatest recurrence of the lesion after 6 months follow up.

Fig. 3 A multilobulated dermal lesion consisting Fig. 1 A solitary large nodule on the anterior of loosely arranged spindle and stellate cells aspect of left leg. within abundant stromal mucin (H&E x40).

Fig. 4 Many cells had thin, delicate net-like Fig 2 A well defined exophytic nodule with projections imparting a sheaf-like configuration smooth glistening surface. (H&E x400).

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Although NT is rare in the lower extremity, the clinician should consider this entity in the differential diagnoses, as it is imperative to distinguish it from malignant lesions so that aggressive therapy could be avoided.11 Three variants of nerve sheath myxoma were described based on histopathological evaluation. These subtypes included the myxoid type, the cellular type and the mixed type. The classical Fig. 5 Immunohistochemistry showed strong myxoid type is characterized by low cellularity immunoreactivity of infiltrating cells with S-100 and large amounts of myxoid matrix. The lesion stain. is usually bordered and diffusely positive for S-100.12 As in our case, the strong positivity of DISCUSSION tumor cells for S-100, which is a well-established Neurothekeoma is a benign skin tumor that marker for Schwann cells and myelin sheath, is usually related to a myxoid neoplasm of the favors the Schwann cell origin. The cellular soft tissue with presumed neural differentiation. types of nerve sheath myxoma typically are not The cytological differentials include nerve well circumscribed, and the mixed type includes sheath myxoma, mixed neurothekeoma, myxoid varied cellularity with focal myxoid regions. neurofibroma, plexiform neurofibroma, myxoid The differential diagnoses include schwannoma schwannoma, extraneural perineuriomas, (also the malignant type), neurofibroma, cutaneous myxoma, intramuscular and juxta- neurilemmoma, leiomyoma, intramuscular articular myxomas, cutaneous mucinosis, myxoma and low-grade .13 and hamartomas. All these lesions show Reviewing the reported cases of nerve sheath myxoid material along with benign spindle to myxoma, a consistent immunohistochemical stellate cells on cytology. Histopathology and profile of the three histopathologic variants has immunohistochemical examinations are extremely not been established. Schortinghuis14 reported a important in arriving at the right diagnosis. myxoid case of nerve sheath myxoma which was Because of rarity of other entities, spindle cell negative for S100 while the myxoid nerve sheath neoplasm probably myxoid neurofibroma was myxoma cases reported by Nishioka15 and Makino offered as the first cytological diagnosis.6 16 were S100 and NSE positive. Penarrocha17 and Amongst the few cases reported in the lower Nishioka et al.15 reported two mixed-type cases, limb, foot,7 hallux8 and subungual location in the which were positive for both S100 and NSE. The toe9 have been described in literature. Another diagnosis of the cellular variant was given for one case reported in the ankle of a 62-year-old man of the three oral cases reported by Nishioka et showed extensive dystrophic calcification within al.15 That cellular lesion was both S100 and NSE the lobules of the tumor, which had prompted positive. The other two cases reported by Nishioka a misdiagnosis of foreign body granuloma.10 et al. were of classic and mixed variants and all

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showed the same S100 and NSE immunoprofile.15 sheath myxoma of the hallux: a case report . Foot Ankle Local excision is the treatment of choice for NSM. Int 1994; 12:666-68. 9. Connolly M, Hickey JR, Intzedy L, Pawade J, de Recurrence is rarely reported after local excision. Berker DA. Subungual neurothekeoma. JAAD 2005; In summary, this case report describes the 6th 1:159-62. reported case of lower limb nerve sheath myxoma 10. Goette DK. Calcifying neurothekeoma. J Dermatol and the first giant case presenting in the literature. Surg Oncol 1986; 9:958-60. 11. Bergamin F1, Gangemi EN2, Cerato C2, Clemente A2, Borsetti M2, Suriani A3, Taraglio S3. An unusual REFERENCES case of neurothekeoma of the arm in an adult. J Orthop 1. Harkin JC, Reed RJ. Tumors of the peripheral nervous Traumatol. 2016 Sep; 17(3):287-90. system. In: Atlas of tumor pathology,AFIP,2nd 12. Lee D., Suh Y.L., Han J., Kim E.S. Spinal nerve sheath ed,Washington DC, 1969, p60. myxoma (neurothekeoma) Pathol Int. 2006; 56(March 2. Gallager RL, Helwig EB. Neurothekeoma: a benign (3):144-49. cutaneous tumor of neural origin. Am J Clin Pathol 13. Akhtar K., Zaheer S., Ray P.S., Sherwani R.K. Myxoid 1980; 74:759. neurothekeoma: a rare soft tissue tumor of hand in a 3. Kim BW, Won CH, Chang SE, Lee MW A case of nerve male toddler. Niger J Surg. 2013 Jan; 19(1):32–34. sheath myxoma on finger. Indian J Dermatol. 2014 Jan; 14. Schortinghuis J, Hille JJ, Singh S. Intraoral myxoid 59 (1):99-101. nerve sheath tumour. Oral Dis. 2001 May; 7(3):196-99. 4. KA Levin, R Hayden, CA Hanau, LM Galindo. 15. Nishioka M, Aguirre RL, Ishikawa A, Nagumo Cytologic findings of myxoid neurothekeoma: case K, Wang LH, Okada N Nerve sheath myxoma report based on fine-needle aspiration cytology, (neurothekeoma) arising in the oral cavity: histological immunohistochemistry, and correlating histopathology. and immunohistochemical features of 3 cases. Oral Diagn Cytopathol. 2002; 27:173-76. Surg Oral Med Oral Pathol Oral Radiol Endod. 2009 5. Avninder S, Ramesh V, Vermani S. Benign nerve sheath May; 107(5):e28-33. myxoma (myxoid neurothekeoma) in the leg. Dermatol 16. Makino T, Utsunomiya T, Kamino Y, Kobayashi R, Online J. 2007 May 1; 13(2):14. Fukumoto M, Yamamoto H, Nagura H Review Nerve 6. Bhat A, Narasimha A, Vijay C, Sundeep Vk, Nerve sheath myxoma of the tongue in a child. Int J Oral sheath myxoma: report of a rare case. J Clin Diagn Res. Maxillofac Surg. 2002 Aug; 31(4):451-54. 2015 Apr; 9(4):ED07-9. 17. Peñarrocha M, Bonet J, Minguez JM, Vera F. Review 7. Pesrich G, Portela M. Neurothekeoma in the foot: a rare Nerve sheath myxoma (neurothekeoma) in the tongue occurrence. J Am Podiatr Med Assoc 2004; 94:59-60. of a newborn. Oral Surg Oral Med Oral Pathol Oral 8. Gehrke JC , Hamson KR, Havey AD. Dermal nerve Radiol Endod. 2000 Jul; 90(1):74-7.

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